One of the ongoing fallacies in the medical profession is that a small volume nebulizer (SVN) works better at delivering medicine than a metered dose inhaler (MDI). The truth is, with proper technique, they both were equally well.
Still, even thought the AARC's "A Guide to Aerosol Drug Delivery," notes that the dose of a medicine delivered with an SVN is two times greater than 2 puffs of an MDI, this doesn't matter: the end result is the same.
The guidelines note the following: "Clinically it is often thought that nebulizers may be more effective than MDIs, especially for short-acting bronchodilators in acute exacerbations of airflow obstruction. A number of studies have established that either device can be equally effective, if the lower nominal dose with an MDI is offset by increasing the number of actuations (“puffs”) to lung dose equivalence."
Thus, one test showed that 5 puffs of terbutaline had an effect on FEV1 (the best indicator on a bronchodilator's efficacy on obstructed lungs) as 2.5 mg of terbutaline given via SVN. So it's clear that an MDI is equally as effective as an SVN.
This is true "provided that the patient can use the device correctly."